1. Field of the Invention
The present invention relates to a non-dispersion type infrared analyzer and in particular to an infrared analyzer which can simultaneously determine plural components in a fluid sample by means of only one analyzer.
2. Description of the Prior Art
The conventional method in which plural components are simultaneously determined by a single analyzer encounter more problems than the method in which only one component is determined by a single analyzer. For example, phase adjustments and optical adjustments are required when plural detectors are used. Also, a zero drift adjustment is required for each detector because drift causing factors such as a change in the light intensity, contaminants soiling the cells or the like cause different effects upon the different components to be determined. For example, in the conventional non-dispersion type infrared analyzer for determining plural components as shown in FIG. 1, the optical adjustment is carried out by locating screens 2 between detectors 1 and consequently a large space is required and the spatial losses are large
Furthermore, the harmful effects of zero drift must be overcome by carefully carrying out the electrical adjustment of each detector 1. But, one adjustment is not enough and the time consuming troublesome adjustment is repeatedly required. Also, any slight deviation in the placement of the center of rotation of a chopper 3 leads to a deviation in the angle at which the blades of the chopper cut the two light paths 4, 5 and accordingly result a poor S/N ratio. As a result, in the case when a fluid sample has one high content component and one low content component, even though the high content component can be determined, the other low content component cannot be determined unless the length of the cell is changed. As described above, the contents of components to be determined in a fluid sample are generally different and accordingly the above described analyzer has a serious problem that it can only be applied for the case in which the fluid sample has components to be determined having almost the same concentration. Conversely, the use of the above-described analyzer with the above-described usual fluid sample leads to significant differences in the sensitivity and accuracy of detectors 1, such differences resulting in a fatal defect with respect to the analyzer component determination. Furthermore, in the case when plural components are to be determined, it is necessary to compensate each output from each detector with the output of every other detector, as shown in the specification of U.S. Pat. No. 3,898,462, because the characteristic absorption bands of components to be determined may frequently overlap each other so as to interfere with each other. In addition, the adjustment of the above-described compensation must be repeated for every zero adjustment and adjustment of the phases and accordingly, the analyzer operation is unusually troublesome when a deviation occurs in the zero drift and phases.